Operation Manual

Basic Design of ISDN-WANs and Configuration Overview 73
Choose Static Routes to Link Networks with Static "Nature"
Classic and Dynamic ISDN Interface Usage with Static Routes/Services
Routing Protocols
When setting up your WAN links over ISDN, have a look at your
LAN and the LANs that you wanto to interconnect over your router
and decide whether they are of a more static or dynamic nature.
Whenever they are more static, it is recommended to use static
routes/service instead of a routing protocol to link them over ISDN,
disregarding whether you use IPX, TCP/IP or AppleTalk.
Further recommendations that go together with static routes/
services:
- First, configure only those routes/services of your local and of
each remote site on your router that are required for your
internetworking purposes
- Second, use FILTCFG to filter out single IPX nodes, IP hosts,
NICs, packet types and for IP in additon IP services (e.g. telnet,
ftp) that are on those routes you configured, but shall not gain
access to remote sites over ISDN or be transmitted over ISDN.
Note that for servers/services that only need to be available
sometimes, it can be more comfortable if you configure the
routes/services once and use FILTCFG to filter them out or let
them pass through.
The recommendation to use static routes/services further applies
irrespective of whether you want to set up classic WAN links or use
ISDN interfaces dynamically. The only difference is, that with dy-
namic ISDN interface usage, you will configure more than one Call
Destination over an ISDN interface and will set the Disconnect
Timeout for each of these Call Destinations to release the ISDN
interface. Be aware that first, the Disconnect Timeout is the only
method to release an ISDN interface that makes sense with static
routes/services, and, further read through the section "Choose
Routing Protocols to Link Networks With Dynamic ´Nature´" care-
fully to know about what you have to consider with dynamic ISDN
interface usage.
With routing protocols, advantage and drawback are "turned
around": Using a routing protocol instead of static routes/services
configuration overview.pm6 28.05.97, 00:0373